The present invention relates to sealing arrangements in axial-flow turbomachines to minimize leakage of gases. More particularly, the present invention relates to a sealing arrangement between a turbomachine rotor blade and a rotor disk to minimize cross-stage leakage flow between the blade and the rotor.
Modern gas turbine engines generally include an axial-flow compressor and an axial-flow turbine, among other components. Each of the compressor and turbine includes one or more rotor disks, and each rotor disk carries a plurality of peripherally-positioned, circumferentially-spaced rotor blades. The rotor blades in a compressor are adapted to act on incoming air to increase its pressure by compressing it, and the rotor blades in a turbine are adapted to be driven by hot combustion products, and in the process they take energy from the combustion products. In each case, however, there is a pressure differential across the rotor blade in the axial direction of the gas flow, and consequently there is the possibility of undesirable leakage flow that can take place between the upstream and downstream portions of the rotor.
One such possible leakage path exists at the interconnection between the rotor blades and the rotor disk, where there is a small gap between the blade base member, usually a dovetail design, and the rotor disk groove in which the rotor blades are carried. Accordingly, in some gas turbine engines small diameter seal wires are employed and are positioned between the blade platform and the outer periphery of the rotor disk in an effort to seal the upstream and downstream areas at the connections between the rotor blades and the rotor disks to thereby block leakage flow. The seal wires are split and can therefore expand in a radial direction of the rotor when under the influence of centrifugal force. Such seal wires serve to minimize leakage gas flow from the high-pressure region of the flow path to the low-pressure region, and thereby maintain the maximum mass flow of the gas flow stream to maintain the operating efficiency of the engine.
The various rotating parts of a gas turbine engine are subjected to centrifugal loads during engine operation. Such centrifugal loads can be continuous loads and they can also be alternating loads. The rotor disk can expand because of thermally-induced loads as well as mechanically-induced, centrifugal loads. Thus, a split seal wire will be able to expand and contract during engine operating cycles, producing relative motion against the rotor blade platform while there is contact pressure therebetween. The expansion and contraction produces cyclic rubbing of the seal wire against the platform, in addition to vibratory rubbing motion because of blade platform vibration in a radial direction of the rotor. The relative motion between the rotor blade and the seal wire results in blade platform wear that manifests itself in an irregular wear groove pattern on the inner surface of the blade platform, and such wear results in gaps in the area where the seal wire contacts the blade platforms and rotor disks during engine operation. The formation of such gaps, as a consequence of the resulting enlargement of a portion of the leakage flow passageway resulting from the blade platform wear, leads to increased leakage flow, which can result in diminished engine performance.
It is therefore desirable to provide a blade platform having a seal-wire-contacting surface that is configured to control the seating location of the seal wire, in order to reduce platform wear and maintain blockage of the gas leakage path, to thereby maintain an effective sealing relationship in order to minimize leakage gas flow.
Briefly stated, in accordance with one aspect of the present invention, a turbomachine rotor blade is provided with at least one seal wire groove. The rotor blade includes a base member having a longitudinal axis and a transverse axis. A platform is carried by the base member and extends generally transversely relative to the longitudinal axis. An airfoil extends in a longitudinal direction from the platform and on a side of the platform opposite from the base member. The platform includes at least one seal wire groove adjacent to the base member, and the seal wire groove is defined by a concave section for receiving a peripheral surface of a seal wire. The seal wire groove also includes a ramp section extending from the concave section and inclined relative to the base member transverse axis to guide movement of the seal wire toward the concave section.